Fluid actuated impact tool



Nov. 11, 1958 R. BAsslNGER ETAL 2,859,733

FLUIDACTUATED IMPACT Toor.

Filed Nov. 23, 1955 4 Sheets-Sheet 1 Nov. 11, 1958 Filed Nov. 23, 1955 R. BAssxNsER Er-AL FLUID ACTUATED IMPACT TOOL 4 Sheets-Sheet l5` R055 .Bass/nger'- z/ames @afa/ner INVENTOR.)`

[wf/@W A fr0/wf ya United .States g PatentA .This invention relates 4to a.l uid .actuated impact tool of the type vwhich ,is .particularly adapted. to ..be.-operated by .apneumatic .medium such ascompressedair Aor steam.

4In one ofits aspects, -.it .relateswto a tool of -such type .particularly fadapted-for digging .holes Iin .quarrying .opera- Ationsand the like.

The improved impact ztool .of' this .invention is of-.the type which employs .a `compressible lluidjto. power :the -toolz.and:.-to idrive .a :hammer tin both its powerfandreturn strokes. The :tool is also .characterized by its.construc tion -which.;permits it :to rhave .'acutting tool such as .a `.bit

connected to itsanvil at a relatively. shorttdistance from' the impact face .of the anvilnso .that .in operation, the ytool Acan follow :the ,cutting bit down aiborehole of substantial depth as the latter is dug so that increasedzefciency .of ,energy delivery gto .the/bit .isfrealized ln .accordance through is controlled ,iby a novel 4valving arrangement and the exhaustffluid; isv directedsthrough the` bitfto .-a-.point .adjacent the workingiace-ofthehole in .order tocan-Y cuttings from the hole. f

the bore hole.

PaltentedNov. 11, 1958 `tered Vwhich may, despite the best eiorts ofthe opera-tor, permit the bit to drop or drill away from the supporting structure until the sliding connection is extended .to its limit -so that the-.bit is supported by the supporting structure. "The same thing may happen if the drillingv rate exceeds .the rate at which the supportingstructure .(le. g. drill string) is fed into the hole so that the bit drills away from the supporting structure .until its slidinglconnection therewith is fully extended. As a result, continued beat- Aing of the hammer on .the anvil causes the percussive `.energyto be delivered through .the .connection .to the supporting structure with consequent damage .to the same. This should be avoided.. However, .at .the same time, .provisionshould be made to conduct the .exhaust .power fluid to the bit so that it can sweep earthen cuttingsfrom Accordingly, special .provision ymust be made to do `this while .at the same .time not aggravating lor preventing vthe solution of fthe other 'problemsencountered in the .operation of a percussion tool ina -bore hole.

Also, it is usually desirable and in many cases necessary to .rotate the bit `during the Vdrilling .operation so :thatit is indexed to take a new bite out ofthe .bottom .of theborehole. The torquefor rotation of ithebit-must be transmitted from the drill string across .the .impact tool to the bit and such transmission shouldbe accomplished Withoutcausing the `hammerqto bind.` At the same time, .thehammen the. power `lluid .supply conduit andthe :anvil :must be maintained. in proper axial alignment. `lhese .problems of torque transmission .and axial. alignment, .if not properly.solved.4 can cause .considerabledicnltn parltieularly in quarry operations. Eorexamplethebitzmay In .the pashmany .types vof pneumatic tools. have been devised for various purposes such as pavement breakers and vthe like. In thefmainrzthese tnolshave. been. usedY to perform ,certain operations at ythe 'earths surface shutom have been `used to d-ri1 l (hol es inthelearthrpaltielllally holes having a very small gauge and which are shallow. Such ltools` usually embody a hammer-whichremains at the .surface ofthe learth and impact ,energy -from-ftheqhain: mer .is transmittedto `the fbit bylneans `'otra-rod which extends intothenhole between the.V bit andthe percussion tool. As the drilling 'operation proceeds, additional lengths .of vrod .are needed -to Ypermit 4the-percussion tool to `tenlan at the surface. Accordingly, theaeieienoy.- of these tools decreases as the dept l 1.. of .drilling 1increases due. tofthegreater. amounts :of frrlpaetenergyilost ,in fthe increasing length of rods. Also, the use ofsu,c h.;rod,s d enitely limits the amount .of .energy which. c n be delivered to the bit since inereasingaenergy input results inrod.failure.usuallylay-fatigue. 1 I

. .When `a ,conventional 4vimpact .tool is. .lowered into.a bore hole, several ',problems .immediately arise, which problems .are not existent when .the .tool ,remains atthe surface of .the earth. .lntheiirst jplac e,the tool .is down the hole where it-cannot b e .observed by an .operator .t o control it. The ,operatormustfeed thexdrillstring into the hole ata .ratesubstantially equal tothe drilling..rate. If he 4eeds'too. fast,: the..i ncr .ease in. bottom .hole weight 0n the bit isapt to cause-a .Crooked .holeand .make-im dexing (rotation) ot the bit ditlicult. v If he; feeds,..to o vslowly,.,the...harnm'er delivers energy .to the tool .housing rather than. to A'the bit.' Thus, for example, it, is .desirable that the .anvil .have a. limited. slidingconnection .with .the supporting structure..thereforinstead of .a .Xed .connection so Athat,in operation...thedmpact energy generated by the hammer is ,delivered through .the .anvil .to ythe .bitinsteadkof to the .supporting- `struct-ure. In `many v.,drllingfoperations, fissures or Caverns or soft formations are encoun- ,encounter a sharply inclined face of .a formationco that .it tends :to follow Such face and ldiga.crooked...hole-v To maintain Vthe bit in proper alignment imposesconsider- ,able laterally acting stresses onthetool vand thesestresses should not vinterfere with the h amincls operation. Eurther, the bit may Vencounter acavernr o r fissure o f such size that .the bit becomes wedged therein to an extent it. cannot be rotated. In such case, `the fharnrner ,must remain substantially `free to deliver percussive energy to the bit and -yet be under complete .control of 4the. operator at all times. One reason why the hammershould always b e substantially unhinderedin its action despite difficulties the bit may encounter is-,that in drilling la hole by means of percussion while rotating Aa bit, they actual sizeof .the hole must be somewhat larger than the Aigauge of the :bit so that the latter remains free-.to .be rotated. The .drilling of the oversize holes is accomplished when the hammer delivers, ateach blow, suicientgperussive energy to the bit; delivery of .lesser energy causes the l, hole sizeto decrease. In view of this, it is desirable that the hammer be able to deliver substantially..undiminished percussive .energy to the bit despite vthe latter vencountering wedging fissures, inclined formations or the. like.

Another problem encountered when an impact-tool is lowered into a bore hole is thatof earthen.cuttingsinterfering with the tools operation. For example, if a cutting falls on theanvil face, much of the forceoffthe .hammer is concentrated at the cuttingsince it representsa raised area on the anvil. Also, cuttings can build uplinevenly on the anvil face so that the hammer cannot properly distribute the energy it delivers across the entire area of the anvil face. This can result in spalling of the anvil and hammer faces. Also, cuttings may lodge in valves or between the piston and cylinder surfaces of the tool and` thereby interfere with the proper .operation ofthe tool. i Accordingly, it is desirable to. exclude cuttings from theimpactftool at all times.

Thus, it can be seen that in addition to mechanical PrQblems'there is the very real` problem ofcontrolling the delivery of .impact energy to the bit vi ns,u chV a manner. that not only is such delivery under the control of the operator at all times but also, in the event unforeseen .same for increased efliciency of percussive energy delivery to the bit.

Another object is to provide a compressible fluid pow- -ered impact tool constructed and arranged so that the percussive energy delivered by the hammer to the anvil is automatically decreased should a working face to which .the anvil delivers percussive energy decrease its resistance to movement of the anvil to thereby avoid transmission vof excessive percussive energy to the supporting structure for the anvil.

Another object is to provide such a tool in which move- Yment of the anvil to extend a sliding connection thereof with the supporting structure for the anvil not only perymits variation in the amount of percussive energy delivered by the hammer but also permits torque to be transmitted from the supporting structure to the anvil without substantially interfering with the hammers operation iin such a manner as to reduce the energy delivered thereby so that the tool can be easily and safely operated under many conditions.

Another object is to provide such an impact tool in which such connection not only accomplishes the foregoing functions but also maintains the anvil in proper axial alignment with the remainder of the impact tool vwithout imposing binding stresses on the hammer so that a desired quantum of percussive energy can be delivered to the anvil at all times despite lateral stresses applied to a working tool carried by the anvil which stresses tend to cause axial misalignment of the parts of the impact tool.

Another object of the invention is to provide a com- Apressible fluid powered impact tool in which provision is made to exhaust power uid through the anvil from an enclosure preventing cuttings or the like from falling upon the anvil face so that the exhausted fluid can carry the cuttings from the vicinity of the tool as such cuttings are loosened by the Atool from a working surface to which the tool is delivering percussive energy.

Another object is to provide a compressible fluid powered impact tool in which the hammer is enclosed in a case carried by the uid supply conduit to be reciprocated in both its power and return strokes by the power uid which is ultimately exhausted through the anvil, such exhaust and the application of power fluid to the hammer being controlled by valve means in such a manner that the timing of the impulses applied to the hammer by the power uid to move the hammer are made dependent upon the extent of movement of the hammer with respect to the anvil so that by making the anvil movable relative to the case, the beating frequency of the hammer can be Another obiect is to provide such a tool in which movement of the fluid supply conduit with respect to the anvil to increase the beating frequency of the hammer is limited Vso that the tool can be simply operated at a tixed beating frequency.

Another object is to provide such a tool in which the anvil can move relative to the supply conduit between a limit which udefines a desired beating frequency and therefore power delivery of the hammer and another limit at which the hammer delivers very little, if any, energy to the anvil whereby operation of the tool is made safe yet flexible without necessarily mechanically altering its component parts.

Y Another object is to provide a compressible fluid powered impact tool in which the application @f SUCh 'uid to the hammer to move'it in its return stroke is `controlled by a nger type valve element xed to the hammer and cooperating with an exhaust port in the anvil to control such applicationlwhereby not only is the beating frequency controllable as aforesaid but also it is possible by suitable manipulation to prevent the hammer from delivering substantially any energy to the anvil even though the full pressure of the actuating iluid continues to be applied.

Another object is to provide such a tool in which there is an arrangement for preventing the finger from fatiguing and yet the valve action is decisive and sharp so as to prevent mushing of the hammer in its operation.

Another object is to provide a compressible iluid powered impact tool which in its normal operation only has one moving part so that it is simple in construction and which can be merely set down on a working surface and operated with a predetermined energy output and yet if the resistance of the working surface suddenly decreases, the energy output likewise decreases.

Another object is to provide such a type'of tool wherein the sliding connection between the anvil and supporting structure therefor is such that the anvil can be made unitary with the bit so as to eliminate any joint therebetween which could fail when enormous amounts of percussive energy are delivered to the bit.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specification, the appended claims and the attached drawings wherein:

Figs. 1, 2 and 3 are schematic illustrations of the operation of an impact tool constructed in accordance with this invention;

Figs. 4A and 4B illustrate, partially in section and partially in elevation, one embodiment of an impact tool constructed inaccordance with this invention; it being understood that these gures are continuations of one of the other with Fig. 4A showing one end of the tool and Fig. 4B showing the other end;

Fig. 5 is a cross-sectional view taken on line-5-5 of Fig. 4B;

Fig. 6 shows a more preferred an alternative form for the lower portion of the tool, the portion of the tool in Fig. 6 being substitutable for the portion shown in Fig. 4B;

Fig. 7 shows a more preferred and alternative form for the upper valve means and the illustrated portion is substitutable for the corresponding portion in Fig. 4A;

A Fig. 8 shows an alternative arrangement of the lower end of the hammer;

v Fig. 9 illustrates an arrangement permitting the tool of this invention to be submerged in water or other liquid during its operation; and

Fig. 10 is a perspective of a valve shown in Fig. 9 in cross-section.

Like characters of reference are used throughout the several views to designate like parts.

Generally, theillustrated apparatus of this invention includes a hammer 10 mounted for reciprocation within and relative to a fluid supply conduit means, designated generally by the numeral 11, to deliver impact blows to an anvil 12 bystriking hammer face 13 against anvil face 14. In the preferred form, the tool includes an upper and a lower valve means 15 and 16 preferably arranged so that upon closing the upper valve means and opening the lower valve means, the hammer is moved by the pres- 'sure of resilient (compressible) fluid from supply conduit means 11 in a power stroke to ultimately deliver a blow to the anvil. Then upon opening of the upper valve means and with the `lower one closed, the pressure of the power uid acts to move the hammer in a return stroke to complete the cycle. In order to conserve power fluid, the arrangement is such, as will be explained in detail below, that at least one of the valve means restricts flow through the tool at substantially all times so that free ow S "of ,fluid .without exerting adesired actuating. force on .the hammerisprevented C Turning now toV ay detailed .description of the Vtool illustrated in Figs. 4A and 4B, the fluid supply conduit means ancornprise anupper valvesub 1.7. having.a central bore 18 therethrough andbeing provided withabox or other connecting means .at its. upper fend. (not vshown) .for .connection with adrill sjtring' tothatnot. only .can power fluid 'be conducted" to vthe t-ol through the drill string ,but .the latter can act to lower the...tool fintothe borehole, .rotate 'it and otherwise. govern Iits operation therein. .Also included as a..p.arto'f the. .liuidsupply cond-uitmeans vis a cylinder or an extending casing .portion made .up of an .upper cylinder .sub .1'9 .and alowercylinder sub l0, both "ixedly connected to upper valve sub .17 Yas 4by means .of "threa'dsfZl and 22. v n Hammer .'lft) .is preferably .of .one-piece construction andis reciprocally disposed within .the upper .and lower cylinder subs. .I9 audit). .It [is .provided .with Asmaller such a manner that the fluid supply conduit means kvand anvil can. lhave limited longitudinal .movement relative to each otherand yet relativerotation ,therebetween is substantiallyprevented. .The purpose of .such' type connection is at. leastfourfold: .(1) .itprovides a torquetransmitting connection for. rotating. the. anvil Aand. a .working r tool, such as '.bit 12a carried thereby, :b y. rotation of -.the .drill string in .order that r the .bit eanbe :indexed .rotationally .'to .take..a..new.bite at..the..working..face ofrthebore hole without;` applyingsuch .torquato .the hammer in -a `manner as to interfere .with..its.reciprocation; (2) Aitpermits .the Ebitto. drop away ordrillawayfrom the fluid -s'upplyconduit means. when .the glatter, .is beingmoved too slowly Ito .keep ,up with :the-bit so.as.to. reduce the impact energy of the .hammer -to .thereby .avoid .damaging the connection .or the lluidsupply conduit Ymeans;y .'(3) .itprovides .a meansfor supporting the anvil-and bit as the toolsisbeing .loweredintothe .bore hole until the.- bit'encounters the working face thereof; .and (=4.) it Lpermits changing :the .beating .frequency `of .the rhammer without withdrawing the .tool from the.boreI hole 'as willbe-.explained in more detail below. l

.In a ypreferred form, the .connecting means comprises anut 27:havinga.threaded'zconnection128 to the Ilower or anvilend pf the flowerrcylinder :suby 20. The `nut is provided with longitudinally :extending vsplineways 29, here .illustrated -asfbeing f'four inv4 number, whichl are radially alignedV with corresponding splineways r30 vin lthe anvil. -Bridging elements, vsuch -'as 'roller bearings 31, are-disposed inthe-splineways to^transmit torque between lower cylinder sub 20 andthe anvil while permitting relative longitudinal movementV therebetween.

In order to hold the anvil in properaxial alignment with Vtheflower cylinder sub without imposing any substantial aligning stresses fon the bridging elements or splineways, theanvil canbe provided withanupperpiston part..32.and another portion-33 having` a closesliding lit within the -lower cylinder suband nut .27. ySince piston partLZY and portion .33 are longitudinallyfspaced apart, they provide axially .aligning :bearing points maintaining the anvil infa-xialialignment Awhen the telescoping joint is colliapsedfas shown yinFig. `4B. As-areSult, lthe anvil cannot only be kept inmueh better axial alignment than would be the-caseif such alignment were 'to '.be. maintained 'solely by ibridging `elements 31 cooperating with theirsplineways'r but also aligning stresses are removed .the .jointis easily .contracted aud extended.

assenze `from `the bridgingrelemeuts and splineways. .As aressult,

.In order that the anvil can .be of .one-piece construction .and .of sutlicient cross-section .as .to withstand .the blows .of the lhammer, nut.2.7 is employed to permit assembly .of vthe toolrandis .longitudinally `split into two or .more :sections .27a (Eig. 5,) `-vlhich..hav,e .abutting .faces .27b. ,'.Splineways;29 in thenut l:and..anvfil arearrngedso that the bridging elements .can be ,placed lin .anvil .splineways 30 and then the nut sections properly positionedtoretain .them in place. -,'I `hus, .one .pair .of .splineways .can be fplacedat .the .split between the..nut.sections and .another .pair .on ardiameter normal .to .the..diameter .through the splineways .at thesplit. .This permitsthenut sections to .be moved .into place .andryettohaveall of .the splineways provided with a.close Yiit..aroundthe .bridgingelements Themas 4.the nut'isv screwed .iutothelower cylinder sub, faces v27h.are.broughtinto clos.e.abutment witheach. other tohold .the 4nut.se.ctior1s inplace without imposing .excessive binding stresses .on .the bridging. elements. Faces 27 b are preferably disposed ona diameterbfthe nut `so as .to .avoid .one .section .of .the .nut urging the-other vinwardly as ,thernutisiightenedzintothecylindersub. ,Pins .27C .can be used :toaid Tin `holding :the nut sections in place .as .the .nutis vb.eing:assembled. Y .As .will be-more ,fully .explained below, Ithe beating frequency: of rthe .hammer I.can be .made -towvary with the .distance .betweenupper valve. .s ub .-17 and :anvil 112. -In order tofacilitateeld `operationf-of the tool ata desired :hammer frequency (i. ..e..at =a.de.sired horsepowerinput .to .the ..bit-), .stop parts Yare provided limiting relative .longitudinal movement. between: the anviland the uid .supply conduit and .can .takethe vform vof an endwise shoulder 34 comprising vthe .lower .fend .of the vnut and .an .outturned .shoulder .35.011 the .-anvil. .Then by merely .applying `enough .force .to keep stop ,parts .-34 and 3 5 in engagement, the Vbeating Afrequency .offthe hammer is xed, the properties .of :thegpower yfluid .remaining constant, at a.predetermined maximum frequencyand a rninimum-of control is.required.to maintainibatsuch maximum over long operational periods.

.The upper end .of spline -sll-.formsan outturned shoulder.36 .on .the .anvil engageable with ythe Aupper end 37 of .the bridging .elementslto support the anvil in the lower cylinder sub asthe vtool'is being -lowered into the bore hole.

Toactuate the hammer, .it is provided `with an area disposed so that pressure 4liuid from .the supply conduit .means can effectively act (here shown to act con.- stantly) .,thereagainst -to .move .th-e hammer in a power stroke toward the 4anvil and iralso with another.and.larger area disposed in an opposite manner lso that pressure iiuidtderivedfrom .fthe supplyconduitmeans can act t0 urge the hammer'in areturn-Astrokeaway fromthe anvil. Valve means are also provided to vary the degree of huid communication betweenithe-supply conduit andthe larger area ,and'between the larger area and the exterior of the tool. By proper sequential operation of these valve means, the pressure of the fluid exerted on the larger area can be increased to move :the hammer in its return stroke against the .force exerted by pressure fluid acting on all or a part of .the smaller area .and then decreased to permit .movement of the hammer'in its power stroke by pressure iluidacting on. the smaller area.

Thus, the annular area shown as the upper end 3S of lhammer piston portion 23 can serve. as the smaller area against which .fluid .frombore 18 ,and passages 39. acts to urge. the hammer downwardly .during its power stroke. In the construction shown, pressure is exerted: on the smaller area at alltimes. Piston portion 23 can. have a plurality of labyrinthgrooves40 to aid-inlimiting flow past the piston from valvechamber 41 into chamber 42. Leakage past the :piston portion can be perf mitted vto su.ch.an extent vthat- :flow .will alwaysoecur from chamber 42 outwardly through passages 42a irrespective Ystoppage of flow. '44 is in the form of a finger-like part fixedly connected 7 of whether the hammer is moving upwardly or downwardly. This prevents any cuttings from being sucked Vinto chamber 42 when the hammer moves in its power stroke. In a preferred form, passages 42a are closed with a check valve which is shown in Fig. 4A as an O-ring 42b held in place in groove 42C by its own resiliency. The O-ring shouldflt snugly in its groove 'to prevent backflow through passages 42a and yet should not-be stretched so tautly that an appreciably higher pressure can exist in chamber 42 than exists exteriorly of the tool.

As a part of the valve or flow control means, piston portion 23 is provided with a bore 43 which acts as a valve element by receiving a valve element 44 therein to restrict flow into passage l45 through the piston. Valve element'44 has a sufficiently close flt with bore 43 as to substantially block flow therethrough and labyrinth grooves 46 can be provided in bore 43 to aid in this It will be noted that valve element to upper valve sub 17 in coaxial alignment with bore 43 so that when the hammer moves to within sufficient 'proximity tothe upper valve sub, valve element 44 will enter bore 43 and remain therein until the upward hammer movement is reversed and the hammer moved through a predetermined portion of the power stroke. In this manner, the supply of power fluid, via passage 45 and branches 47, to the lower end of the hammer to act against the larger pressure area of the hammer is made intermittent. The fluid so supplied must be retained within the lower cylinder sub for a predetermined time and then exhausted so that power fluid acting on the smaller area of the hammer can move it in its power stroke. For this, valve member 49 is provided on the hammer in axial alignment with bore f), which also serves as a valve member, leading to an exhaust passage in the anvil. Upon the hammer moving through its power stroke to be within predetermined distance from the anvil, valve member 49 will enter passage 50 and restrict flow therethrough and will continue such restriction as the hammer delivers its blow to the anvil and moves away therefrom in its return stroke through a predetermined portion thereof. Bore 50 can be pro vided with labyrinth grooves 51 to aid in the restriction.

In many uses to which the tool of this invention can be put, it is desirable to use the exhaust fluid from the tool to achieve a further function. For example, in the drilling of bore holes with a bit attached to the tool, the exhaust fluid can be ejected against the working face of the bore hole to lift cuttings therefrom and thence out of the bore hole. In order to permit proper expulsion of the exhaust fluid through the bit and yet permit the tool to operate satisfactorily, a passage 52 is provided through the anvil to communicate with passages 53 in bit 12a so that fluid can be eventually discharged through eyes 54 in the bit.

For the construction shown in the drawings, it will be seen that with valve means 16 open and valve element 44 disposed in bore 43, fluid from bore 18 and the drill string acts on an area equal to the cross-sectional area of piston portion 23 minus the cross-sectional area of valve element 44 to urge the hammer toward the anvil; the force exerted on the hammer by the fluid being equal to the differential pressure across the piston portion 23 multiplied by the difference in cross-sectional areas mentioned above.

However, with valve means 15 open and valve member 49 inserted in bore 5f?, pressure from the supply conduit will act through passage 45 against an annular area equal to the ycross-sectional area of piston portion 24 less the cross-sectional area of valve member 49 to urge the hammer away from the anvil. At such time, the pressure fluid also acts across an area equal to the total cross-sectional area of piston portion 23 to urge the hammer toward the anvil. However, since the annu- `a situation (with upper valve means 15 open), the effec- 'tive differential area must at least be large enough that 'the force exerted by the pressure fluid acting thereagainst lar area on piston portion 24 is .made larger than the total cross-sectional area of piston portion 23, there thereby exists a net differential area acted upon by the pressure fluid'to move the hammer away from the anvil.

Another area equal to and oppositely disposed from this differential area is of course isolated from the pressure of the power fluid and is exposed within chamber 42 to a much lower pressure (usually substantially atmospheric).

Thus, from the foregoing, it will be apparent that with valve means 15 open and valve means 16 closed, the total effective area of all surfaces on the hammer which are exposed to pressure fluid from the supply conduit and which are also disposed so that such fluid can act to urge the hammer away from the anvil must be larger than the total area of all surfaces simultaneously exposed to such pressure fluid and disposed to permit fluid to urge the .hammer toward the anvil. It will also be apparent that this differential in area upon which the pressure fluid effectively acts to move the hammer in its return stroke is situated upstream of valve means 16 and downstream of valve means 15 so that by alternately opening and closing these valve means, the pressure on the effective differential area increases and decreases to respectively move the hammer in its return Ystroke and then to permit it to move in its power stroke under the influence of pressure fluid acting on the smaller area.

In order to lift the hammer against gravity in such 4is greater than the weight of the hammer. However, in a preferred form of this invention, the upper valve 4means 15 closes while the hammer is in its return stroke and before the lower valve means is opened in order lto trap pressure fluid between the closed valve means as shown in Fig. 2. At the instant the upper valve means closes, there does not exist any pressure differential across the cross-sectional area of piston portion 23. However, continued upward movement of the hammer increases the'volume of the space occupied by the fluid trapped between the upper and lower valve means (due to an increase in the volume of cylinder portion 48 between the hammer and anvil as the hammer moves upwardly) and consequently, the trapped fluid expands and decreases in pressure with resultant corresponding delivery of-energy to the rising hammer. As a result, a pressure differential develops across the net crosssectional area of piston portion 23 tending to resist -upward movement of the hammer and this differential of pressure will increase as the hammer moves upwardly. Accordingly, the above-noted differential area must be large enough relative to the volumetric change in the trapped fluid that at the minimum pressure of the latter, sufficient upward force is still developed to move the hammer upwardly against the ever increasing differential across piston portion 23, until such movement of the hammer causes the lower valve means to open. Of course, the arrangement could be such that the net upward force exerted by the trapped fluid would become less than the net downward force on the hammer before the lower valve means opened with reliance on the upward momentum of the hammer to move it far enough away from the anvil to open the lower valve means but it is preferred that the arrangement of areas be such that the net upward force always exceeds the net downward force while both valve means are closed so that the hammers action is made more positive.

In order to give a fuller explanation of the sequence of operation of the valve means and other parts of the illustrated tool, a description of the operation of the tool will be given. As the tool is being lowered into the bore hole, stop parts 36 and 37 will be in engagement `.thereby positioning lbore `fromvalve element JM. As .the tool is loweredu nt'il essere@ a maximum distance `away .theT bit Zrests on thelbottom 'of the .bore hole, and before .s'top .parts 36 and 37 `are disengaged, lfluid can 4be passed through the toolifto flow downwardly through hammer ,pasvsag'e 45. to ,act 4against Athe'lower end of thehammer ,and'move it" upwardlyf The hammer will imov'e'p'- wardly until valve member 49 is withdrawn yfromy br'e 5.0. after which the pressure below the hammer .will be eiihausted .thioughanvil passage 52. -Duringf'its upward-movement, -tne'hamin'erhas acquired some ylimited momentum" and. will continue upwardly until it s decelera'ted. gravity.V VIt will-then -fa ll downwardly/'to again move valve rnemberv49. intoboevt) afterw'hieh the above cycl'e1is repeated. Accordingly, `it shouldfbe apparentthat` with stop parts 36 and V37 in engagement, valve element 44 is positioned sufficiently far enough .awayzfrom the, anvil that the Vpush-upstroke of the hammer plus its overtravel does not move it sufficiently fark to cause valve element 44 to move into -bre43- The fpush-up stroke ofthe hammer vmay be, defined as that distance the hammer travelsin'its return strokev from an anvil striking. position with valve member 49 within bore' 50. Overtravelf can 'bey dciiedas the remainder of the ydistance the Yhammer travels in its return-stroke; that is, after valve member l49 is withdrawn from bore 50 and before the hammer is Areversed to begin its power stroke. Since in the above` sequence ofl operation the total potential percussive energywhich can'lbe developed bythe hammer is due only to "the downward'acceleration of the hammer by gravity, and since the downward movement of the ham# mer Awill`be decelerated by fluid Vpressure actingv there# against when valve element 49 enters bore 5,0 before the hammer strikes'the anvil, the hammer cannot deliver anysubstantial percussive energy to the anvil. In fact, it .cansiinplyshuttle back and forth without ever strikving the anvil and nally reach a static conditionrhoverl ing over the anvil with the lower valve means open just enough to permit escape of `actuating fluid. As a re'sultathe delivery of ,percussive energy from Ythe Vanvil through stop parts 36 and 37 and nut 27 -to the fluid` supply conduit casing portion is either prevented 4or is ata minimum and substantially negligible. This means that anytime the bit is unsupported by a workingsu'r face such as the bottom of the bore hole, delivery of percussive energy by the hammer is automatically decreased to prevent injury to the tool.

As the fluid supply conduit is lowered into the bore holewith the bit "resting ou the bottom thereof, the telscping joint between lower cylinder sub 2Q and the anvilfwill be contracted with movement of the anvilw upwardly into the cylinder sub. As a result, the ham` mer has' a smaller distance to'travel before valve ele-fV ment 44 enters bore 43.' As soon as the supply conduis is lowered sufficientlyto permit this,` pressure Afrom the supply conduitl becomes effective on end 38 to reduce` the overtravel of the' hammer although the push-,iup

stroke remains fixed. This increases the frequency ofl beating ofthe hammer and continued lowering of the fluid. supply conduit will still further increase the fre-A quency of beating.

Eventually', lowering of the drill string will cause stop parts-34 and' 35 to be placed in abutment and this willV fix the beating frequency of the hammer. with the parts positioned as shown lin vFig. l, fluid flows down through hammer passageAS to act on the underside!x thereof and move the hammer upwardly in its return' stroke. In its Fig. 2 position, the hammer has just about completed its push-up stroke but prior to that time, theV upper valve means 15-is closed so that completion of thep` push-up Ystroke is dependentV uponexpansion of fluid` Thus, startingV ,cvertfavel aus te its momentum. During supi; aver travel,-powe fluid acting against the llower end- 'of the v-l'iafni'nei exhausted through -the anvil and b it sothatjla -Afull .differentialfofbtluid pressure can Vbe, appliedjaeross :upper piston portion `2.3L krlr[his differentiall reverses the directionofnmoyement ofthe'hammerand moves it downwardly in 1its..power3stroke'toward the anvil :as shown in Fig. 3. Before the anvilis struck, however, the lower valvemeansclyoses but this doesnot provide any substantia-1 impediment to the lhammer striking `the anvil (because only low pressure gas `istrapped between the hammer and anvil. Alfter Ithe lower valve means is closed and before the `hammer strikes the anvil, lthe upper valvemeans is opened-by thehammer'movin'g bore 43from around valve :element 44. The hammer continues its downward 4,travel under its own `momentumand at the Sametime pressure fluidI flows downward through the hammer` passage to again :nove` the "hammerin `its return stroke after ithas struck the'anvilfFig. l).

Fromthe foregoing, it is apparentthatwith stop parts `34 and 35 engaged, the distance between the Alower end of valve'membe`r49'and the entrance to bore 43 is :greater than the distance betweenzthe lower end of valve element 44. and-entry to-bore'50 Vso that one ofthe valvemeansis closed .atallitimes In this connection, it should be noted that the length ofva'lve member 49 determines the push'- up'strokegofthel-hammer-so `thatin operation, the hammerwill-alwaysfmove atleast a distance corresponding to the PuShu stroke.

lAs -indicated;above, varying the distance between the supplyconduit-and the'anv'il willresult'in a `variationof the beating4 frequency of the hammer. Thus,^by lowering the"suppl57conduit toward the anvil (assuming stopparts 34-and'3`5'have n otyet'been engaged) theupper'valve; means can bemade tosclose earlier in the push-up stroke so that thefeigtent of hammer travel lwith fluid trapped be;- tween the nvalve means can be adjusted. However, yit; shouldbenotedthat'thereturn stroke ofthe hammer will7 always be equal'to thexed push-up distance jplus the overtraveldistancel In effect then, varyinglthefpositiron of the'supply conduit ychanges only the overtravel distarix., Thus', ai maximum overtravel will be secured lwhenthe' upper valveelernent 44 is positioned so that it passeshinto; bore 43 little Vbefore or at substantially the Sametime the lower valve means is opened. The reason for this is' that full fluid supply conduit pressure is appliedto movev the hammer upwardly during substantially all of the pushup distance portion lof the return stroke. This gives the hammer increased upward momentum so that the over-A travel",increases',also.v4 i Conversely, with the fluid supplyV conduit lowered toja position such that the uppervalye` means -closesdu'ring the early part of the return strokeT andat a point after which the hammer must continue.L travelling'upwa'rdly a considerable distance before the lower valve means is opened, the pressure trapped be' tween the two valve means will be considerably reduced (by expansion) below the full supplypressure, As a yre-.` sult, the average force acting to urge the hammer. upf. wardly'duri'ng thepush-up stroke is less and, accordingly, thefhammerhasless upwardmomentum atrthe time ,then lower valve means opens so Vthat `the overtrayel. is defv creased: Brslqkinggoit G11-the. drill String sufficiently# that'stbppartsft, arid are always maintainedsin *en-Y:` ga'geme'nt'bythe weight of the drill string, the beating frequency Aof Vthe i hammer will .be fixed.v

mains freer to beat thereon. Further, should the bit encounter an inclined face in the formation so as to tend j Yto follow the same, the parts of the tool are maintained in proper axial alignment without exerting any aligning stresses such as would interfere with free operation of the hammer.

y In connection with the cooperation of bore 43 and valve element 44, it will be noted that piston portions 23 and 24 of the hammer also act as guide elements to maintain bore 43 in proper axial alignment with valve element 44 and since the cylinder portions in which the hammer piston portions reciprocate are rigidly fixed to valve sub 17, the hammer can be very closely maintained in alignment so that clearance between valve element 44 and bore 43 can be made quite small to prevent excessive leakage 1of fluid therethrough. Further, piston portions 23 and 24 of the hammer maintain valve member 49 in axial alignment with bore 50 and piston portion 32 and guide portion 33 of the anvil maintains bore 50 in alignment with the valve member 49. f

It will be noted that since the diameter of piston part 32 in the anvil is equal to the diameter of piston portion 24 on the hammer, the net variation in upward reaction on valve sub 17 and hence on the drill string will be due solely to pressure acting over an area equal to that of valve element 44. Since this area can be made small relative to the cross-sectional area of piston portion 23, the variation in net upward reaction on the drill string is likewise quite small.

It will also be noted that when a drill string or pipe is connected to the fluid supply conduit to supply compressed fiuid thereto, the length of the drill string can be increased as the drilling proceeds by connection of additional lengths thereof to the upper end of the drill string. In this manner, the percussion tool follows the bit down the hole so that the same amount of energy can be transmitted to the bit at any depth of drilling. Also, the distance between the anvil striking face andthe cutting edge of the bit can be made such that a maximum of impact energy from the hammer is delivered to the bit cutting edge and the earth formation. Such distance can be maintained constant instead of increasing with increasing depths of drilling as in conventional pneumatic drills.

It should also be noted that the positive valving action of the tool of this invention permits the hammer to be made of a'relatively small mass and operated at a correspondingly high frequency to deliver the same impact energy to the anvil as would be delivered by heavier hammer operating at a lower frequency. This makes the tool susceptible of increased performance and increased efficiency.

In connection with the valving arrangement -herein employed, it will be appreciated that if it is desired to blow a hole being drilled free from cuttings while ceasing drilling, it is only necessary to lift up on the drill string until the upper valve means remains open. Thereupon, large quantities of fiuid can be blown through the tool to fiush out any accumulated cuttings from the hole. To reassume drilling, the drill string is merely slacked off until stop parts 34 and 35 are again in engagement.

Referring now to Fig. 6, a preferred form of the lower portion of the tool is shown with its parts numbered the same as corresponding parts in Fig. 4B. Although the general operation of the tool is the same as that in Fig. 4B, there are some improvements. Thus, some trouble was experienced with the finger 49 fatiguing and breaking off when it was made of substantial length. To avoid this, finger 49 is hollowed out, as at 49a in Fig. 6, to reduce its mass and also a long radius portion is provided at 49b where the finger joins the hammer. Such long radius portion demands that the upper end of 12 the anvil be changed to accommodate it. It has been found that if the upper end of the anvil is merely provided with a corresponding long radius portion (as indicated at 32a in dashed line), Valve means 16 acts in the fashion of a metering valve.

In other words, as linger 49 is moved upwardly, it permits a gradual increase Vin rate of flow of exhaust fluid from the lower cylinder due to the gradually increasing clearance between the finger and radiused portion 32a. As a result, the pressure in the lower cylinder beneath the hammer is decreased relatively slowly during exhaust thereof so that .the upward travel of the hammer is stopped before the lower-cylinder is completely exhausted. Then as the hammer moves in its power stroke, the fluid trapped therebeneath is compressed to an excessively high pressure thereby robbing the hammer of its potential impact energy. It was found that this decrease in energy delivery to the anvil was in many cases enough that a drilling blow could not be struck.

To avoid this, the upper end of the anvil piston 32 is provided with a counterbore 32b having a substantially square shoulder 32C surrounding bore 50. Then as finger 49 moves upwardly, it clears bore 50 all at once so that the maximum upward force is exerted on the hammer until just the instant finger 49 passes shoulder 32C whereupon the lower cylinder suddenly begins exhausting and can complete the same before the hammer again causes finger 49 to move into bore 50.

Fig. 6 also shows a unitary anvil and bit. In some instances, the use of a relatively heavy (e. g. 60 pound) hammer at normal operating pressures (e. g. 250 p. s. i.) of actuating fluid results in failure at the screwed connection between the bit and anvil of Fig. 4B. To eliminate this, the bit and anvil are made in one piece as shown in Fig. 6. Such arrangement is of further advantage in that transmission of energy to the cutting edges of the bit need not be across a threaded joint which, if not carefully constructed, can result in dissipation of energy.

4 Also, it will be seen in both of Figs. 6 and 7 that seal rings are employed on the hammer and fingers to eliminate the labyrinth grooves of Figs. 4A and 4B and to provide a more effective seal. Also, and of possibly greater importance, the seal rings on the hammer act as wipers to keep the cylinder walls clean and lubricated with oil from the actuating fluid. Thus, seal 40a is located near the lower end of upper piston portion 23 and seal 4Gb near the upper end of lower piston portion 24 so that should any grit or cuttings get into chamber 42, they will be wiped from the cylinder surfaces before the piston portions traverse the same. Seals 44a and 49C are situated near the lower ends of fingers 44 and 49, respectively, to provide a seal with bores 43 and 50 during substantially all of the movement of the p fingers therein. Here again, these seals act as wipers.

The lower outer corners of seals 44a and 49e` are preferably beveled to facilitate their entrance into the bores. Each of seals 40a, 4Gb, 44a and 49e can be of neoprene rubber or the like.

To aid in maintaining the splined joint between the hammer and anvil clean, passages 36a can be provided so that each time lower valve means 16 opens, a puff of actuating fluid will be blown through the joint.

Fig. 7 also illustrates another type of check valve for passages 42a. Thus, an annular ring 42d of neoprene rubber or the like, is disposed about the tool and has a lower end 42e adapted to be flexed outwardly by pressure in passages 42a to relieve the same.

vSome difficulty has been encountered with the hammer fatiguing at the point where passages 47 join passage 45 (Fig. 4A). One manner of avoiding this is to provide the hammer with a diametrical slot 47a connecting with passage 45 as shown in Fig. 6. Slot 47 is preferably elongate in vertical cross-section.

Another manner of avoiding fatigue breaking is shown 13 in Fig. 8. Here the hammer is made in two pieces a and 10b which are held together by a sticking taper'10c1 The lower portion of the hammer is formed with a rounded portion 10d of considerably (e. g. twice) longer radius than that of passage 45. 'Then passages 47 are drilled to intersect at varying points on rounded portion 10d so that in any given cros-section across the lower end of the hammer, there exists more metal than in the corresponding section in Figs. 4A 'and' 4B; A

When the hammer and anvil faces 13 and 14 are made to mate closely together as shown in Fig.` 4B, they have a tendency to act together as a valve and this is especially true when some lubricant is disposed thereon. As a result, it becomes more difficult for the actuating uid to flow inwardly between these faces to move the hammer inwardly in its return stroke and to rapidly flow outwardly justas the hammer strikes the anvil. `Of course, such close mating does not by any means render the tool inoperable since even if the mating faces formed a perfect seal,the; hammer will rebound from the anvil after it has struck the same to permit uid to ovvl in and act on the hammers lower face. Nevertheless, such valving action slows down the hammer. To avoid this, one or both of two arrangements can be employed. Thus, the top of the anvil, or the lower end of the hammer can be slightly crowned as shown in exaggerated form in Fig. 6 or radial grooves 32d can be provided on the upper end of the anvil or the lower end of the hammer. In either manner, the valving action of the faces 13 and 14 will be reduced. i -In some instances, it may be desirable to use the tool of this invention while it is submerged, or. at least the bit is'subrnerged, in water or other liquid. To permitV this'while avoiding liquid back flowing into the tool, a check valve 60 can be provided in the anvil passage as shown in Figs. 9- and 10. While such a valve can take many forms, it must be rapid acting to permit a reasonable hammer frequency and be suciently resilient to withstand many rapid openings and closings. The illustrated valve comprises an elongate lip section 6.1molded so as to normally, when in unstressed condition, be in closed position as shown in the drawings. A rib 62 can be molded onto the lower. end of the lip section to aid in urgingthe lip section to closed position The upper4 end ofthe lip section is annular in cross-sectioniand may be bondedto a metal ring 63. Thelatter can b e clamped in place by an annular nut 64 so that the lip section 62 extends downwardly in the anvil passage to prevent backflow therethrough.

From `the foregoing it will be seen that this invention is oneiwell adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinat'ions are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the `scope of the claims.

- As many possible embodiments maybe made of the invention without departing from the scope thereof, it is to be understood thatall matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. An impact tool powered by a compressible uid which comprises, in combination, anvil means, fluid supply conduit means having a casing portion extending to telescope over the anvil means to enclose therein the striking face of the anvil, a hammer mounted for reciprocation within said casing portion to beat upon the anvil face and having endwise surfaces of different area against whichrfluid pressure from the conduit means can act nto urge the hammer in its power and return strokes, a

rst fluid passageway in the hammer connecting whenl open between said surfaces, a second lluid passageway in the .anvil means connecting the interior of' the 'casing portion between the anvil and hammer with the exterior of the tool, a valve element and a Vvalve member respee tively carried by the conduit means and hammer to operi and close said first and second passageways respectively during finite movement of the hammer in its power and return strokes so that uid pressure from the conduit means is alternately applied to'and exhausted from one ofsaid hammer surfaces, and means providing a slidable connection between said anvil means and casing portion to permit relative longitudinal movement between said valve element and said anvil means so as to vary the beating frequency of the hammer.

2. An impact tool powered by a compressible fluid which comprises, in combination, an anvil, uid supply conduit means including a casing portion extending there'- from to enclose an end ofthe anvil, a piston hammer in said casing portion vand having spaced piston portions of different effective cross-sectional areas, the piston portions slidably engaging saidcasingfportion, 'a first fluid passage carried by one of the casing portions and piston hammer and which when'open vcommunicates between opposite ends of said piston hammer, a second fluid pas.- sage in said anvil for conductinguid from a space be# tween the piston hammer and anvil to the exterior of the. tool, rst valve means including a first valve member carried by the piston hammer and cooperable with a second valve member carried by said anvil'to restrict ow through said second passage while the piston hammer is traveling through a predetermined port-ion of its return stroke from anvil striking position and then to open said second passage during the remainder of the piston hammers return stroke, second valve means controlling ow` through said rst passage including a first valve element cooperable with a second valve element carried by the piston hammer to restrict ow through 4said first passage) upon said piston hammer moving to be within a' prede@` termined distance from said first valve element,` saidl tirst valve element being carried by said conduit means for. movement thereby toward and away from said anviland second valve member to thereby Arespectively increase and decrease the beating frequency of the hammer, and

means slidably connecting the anvil and said casing por-` tion for limited relative longitudinal movement there? between including sto-p parts carried by the anvil and casing portion engageable to limit movement of the conduit means and first valve element toward the anvil whereby the beating frequency 4of the hammer is fixed upon engagement of the stop parts.

3. The tool of claim 2 wherein said connecting means permits movement of the anvil away from the conduit means a sufficient distance that said second valve meansV remains open during any movement of the hammer in its return stroke whereby the hammer is moved in its power stroke with insuflicient velocity to strike a blow to said anvil of sucient magnitude as to damage said con'- necting means.

4. In an impact tool powered by a compressible fluid,

an anvil, cylinder means having smaller and larger diameter portions, a hammer reciprocally disposed in the cylinder means to beat upon the anvil and having' a smaller diameter piston in the smaller diameter cylinder means portion providing a first effective area for driving the hammer in its power stroke and a larger diameter piston in the larger diameter cylinder. means portion pro'- viding a second effective area larger than the rst area l for moving the hammer in its return stroke, said cylinder means, means for intermittently exhausting fluid applied to. said second area including a flow passage through said anvil and valve members respectively carried by the anvll and hammer and cooperable to restrict flow through said passage while the hammer is moving through a predetermined initial portion of its return stroke and then to open said passage to exhaust said iluid, and means slidably connecting said cylinder means to said anvil so that torque can be transmitted to the anvil to rotate the same without application of the torque to the hammer and so that the distance between the valve element carried by the cylinder means and the valvermember carried by the anvil can be varied to vary the beating frequency of the hammer. 5. The tool of claim 4 wherein said slidably connectlng means includes stop parts respectively carried by the anvil and cylinder means for mutual engagement to limit movement of the valve element carried by the cylinder means toward the valve member carried by the anvil to thereby fix maximum beating frequency of the hammer at a predetermined value.

6. The tool of claim 5 wherein said slidably connecting means includes longitudinally extending and radially aligned splineways in the cylinder means and anvil and bridging elements disposed in the splineways to limit relative rotation between the cylinder means and anvil while permitting longitudinal movement therebetween,Y said anvil having longitudinally spaced apart portions having a close sliding t within the anvil end of the cylinder means whereby the anvil is held in axial alignment with the cylinder by said anvil portions without imposing any substantial aligning stresses on the splineways and bridging elements.

7. The tool of claim 5 wherein the slidably connecting means includes a nut threaded into the anvil end of the cylinder means, longitudinally extending and radially aligned splineways of predetermined length in the nut and anvil, and bridging elements of substantially the same cross-sectional dimension as said splineways and disposed in the splineways to limit relative rotation between the nut and anvil, the splineways in the nut terminating short of the ends of the nut, said nut being longitudinally split into sections with adjacent sections having abutting faces preventing the sections from moving radially inwardly when assembled as the nut whereby the sections can be placed around the anvil with the bridging elements in place and then screwed as a unit into the anvil end of the cylinder means.

8. In an impact tool powered by a compressible fluid, an anvil having a piston portion and also having therein a fluid passage connecting between an end of said piston portion and the exterior of the tool, a fluid supply conduit having a casing portion extending to provide a rst cylinder around said anvil piston portion and also providing second and third cylinder portions, a piston hammer disposed within the casing portion with first and second pistons on the hammer reciprocally disposed in said second and third cylinder portions, said second piston element and third cylinder portion being of greater diameter than the iirst piston element and second cylinder portion, a fluid passageway in the hammer connecting between its ends, a valve element carried by the supply conduit to close the hammer passageway upon the hammer moving in its return stroke to be within a predetermined distance from the valve element, a valve member carried by the hammer to close the anvil passage while the hammer is moving through a predetermined initial portion of its return stroke, and means providing a sliding connection between the casing portion and the anvil while limiting relative rotation therebetween whereby torque can be transmitted from the supply conduit to the anvil without application of the torque tothe hammer land whereby the distance between the valve element carried by the supply conduit and the anvil can be varied to vary the beating frequency yof the hammer.

9. The tool of claim 8 wherein said valve member is an elongate iinger-like part movable into said anvil pasif? sage to restrict flow therethrough whenever the hammer is within a predetermined distance of the anvil.

10. The tool of claim 9 wherein said nger-like part is fixed to the hammer against longitudinal movement relative thereto.

ll. The tool of claim 9 wherein said valve element is also an elongate linger-like part movable into the hammer passageway to restrict flow therethrough.

12. `In an impact tool, a Huid supply conduit provided with a cylinder portion extending to telescope over an anvil, a hammer provided in the cylinder portion to reciprocate and beat against the anvil responsive to the application of fluid pressure thereto from the supply conduit under the control of valve means openable and closable responsive to the movement of the hammer, the beating frequency of the hammer varying with the distance between the supply conduit and anvil, a connection between the cylinder portion and the anvil including interengaging slide and guide parts carried by the cylinder portion and the anvil permitting longitudinal sliding movement Vwhile limiting relative rotation therebetween whereby torque canbe transmitted from the supply conduit to the anvil without application of the same to the hammer and yet the distance between the supply conduit and the anvil can be varied to vary the beating frequency of the hammer, and stop parts carried by the cylinder portion and the anvil mutually engageable to limit movement of the supply conduit toward the anvil and thereby fix the maximum beating frequency of the hammer.

13. A tool of claim 12 wherein said anvil includes a piston portion having a close sliding lit within said cylinder portion to close the anvil end thereof and a fluid passageway through the anvil extending between the interior of the cylinder portion and the exterior of the tool, said anvil further havinga second portion longitudinally spaced from said piston portion with a close sliding fit within said cylinder portion, whereby the anvil is maintained in axial alignment with said cylinder portion by said piston portion and said second portion without imposing any substantial aligning stress on the slide and guide parts limiting relative rotation therebetween.

14. The tool of claim 13 wherein a nut is threaded into the anvil end of said cylinder portion and wherein the slide and guide parts limiting relative rotation include longitudinally extending splineways in at least one of the nut and anvil and bridging elements disposed in said splineways and connected to the other of the nut and anvil to limit relative rotation therebetween, said nut being longitudinally split into sections so that such sections can beY passed around the anvil in assembling the bridging elements in the splineways and then screwed as a unit into said anvill end of the cylinder portion to retain the bridging elements and splineways in operative association.

15. An impact tool powered by compressible fluid which comprises, in combination, an anvil having one end provided with connecting means for connection with a working tool, the working tool having a uid flow passage therein for discharge of a fluid adjacent the surface being worked, a fluid supply conduit including a casing portion having aslidable connection with the other end of the anvil, a hammer reciprocally disposed in said casing portion and having rst and second endwise areas with the first area being exposed to uid from said conduit to urge the hammer toward the anvil and with the second area being larger than the rst and disposed so that fluid can act thereagainst to urge the hammer away from the anvil, a first passageway for placing the second area in communication with the conduit, a second passageway disposed in the anvil and when open placing the second area in communication with said ow passage in the working tool, a valve element carried by the hammer restricting flow through said second passageway during at least a portion of the hammers travel in its return J stroke from anvil striking position and upon further -travel of the hammer opening said second passageway,

and valve means openable and closable responsive to movement of the hammer so as to restrict flow through said first passageway while the second passageway is open.

16. An impact tool powered by a compressible uid which comprises, in combination, anvilmeans, fluid supply conduit means having a casing portion extending to telescope over the anvil means to enclose therein the striking face of the anvil, a hammer mounted for reciprocation within said casing portion to beat upon the anvil face and having endwise surfaces against which fiuid pressure from the conduit means can act to urge the hammer in its power and return strokes, a first fiuid passageway connecting when open between said surfaces, a second fiuid passageway connecting the interior of the casing portion between the hammer and anvil with the exterior of the tool, a valve element carried by a part of the conduit means to close said first passageway upon the hammer moving to be within a predetermined distance from said part of the fiuid supply conduit means and then to open said first passageway upon the hammer moving a predetermined distance away from the fluid supply conduit means, a fixed finger carried by the lower end of the hammer to be insertable into said second passageway to govern flow therethrough, said finger being of a length equal to the desired push-up stroke of the hammer, and a limited sliding connection between said casing portion and said anvil.

17. The tool of claim 16 in combination with a check valve in said second passageway permitting ow from said casing portion to the exterior of the tool but preventing ow in a reverse direction.

18. In an impact tool wherein a fiuid supply conduit, a hammer and an anvil are interconnected for reciprocation of the hammer to beat against the anvil responsive to the application of fiuid pressure to the hammer from the supply conduit under the control of valve means openable and closable responsive to the movement of the hammer, the combination therewith of a flow passageway extending through the anvil .from the interior of the tool to the exterior thereof, and a check valve in said passageway limiting fiow to be from the interior of the tool to the `exterior thereof and preventing flow in a reverse direction.

19. In an impact tool wherein a fluid supply conduit, an anvil and a hammer are interconnected for reciprocation of the hammer to beat against the anvil responsive to the application of fiuid pressure to the hammer from the supply conduit, the combination therewith of a flow passageway in the anvil communicating between the exterior of the tool and the interior thereof, a fixed finger carried on the lower end of the hammer for insertion into said passageway to control flow therethrough, said lower end of the hammer being exposed to strike the anvil and against which fiuid pressure from the supply conduit can act with the finger inserted in said passageway to urge the hammer in its return stroke, said finger at its juncture with the hammer flaring outwardly in a long radius portion which smoothly merges with said hammers lower end, and said anvil being provided with a counterbore surrounding said passageway therein and of a depth at least as great as the radius of said long radius portion and providing a sharp cornered shoulder adjacent said finger to permit quick opening and closing of the Valve comprising said finger and passageway.

20. ln ani-impact tool powered by a compressible fiuid which comprises, in combination, an anvil, -uidsupply conduit means including a casing portion ,extending 'therefrom to 'enclose an end of the anvil, a piston hammer insaid casing portion, a first fiuid passage in one of the casing portions and piston hammerwhich when open communicates between opposite ends of said piston hammer, a second fluidpassage in said anvil for conducting fluid from a space between the piston hammer and anyil to V18 the exterior of the tool, said hammer and anvil 4having opposing faces substantially parallel to each other and across which the hammer delivers its impact ,energy to the anvil, a finger extending from a centralrlo'cation on the lower end of the hammer so that theV faceon said hammer is laterally outward thereof, said finger being insertable into said second passage to control fiow'therethrough, a radial groove in one of said faces extending from the inner to the outer edge thereof to permit flow of fiuid therealong whereby valving action of said faces is reduced, and valve means controlling flow through said first passage and openable and 'closable responsive to movement of the hammer to intermittently supply fiuid to the lower end of the hammer to move it in its return stroke. Y

2l. An impact tool powered by a compressible fiuid which comprises, in combination, an anvil, fluid supply conduit means having a casing portion telescoping over the anvil and enclosing therein the striking face of the anvil, a hammer mounted within said casing portion to Vbeat upon the anvil faceand having opposing endwise surfaces upon which fiuid 'from the conduit means can act to move the hammer in its power and return strokes, a first fluid passageway through the hammer, a second fluid passageway through the anvil, a first finger carried by the conduit means to telescope into said first passageway to restrict flow thereinto during movement of the hammer in a final portion of its return stroke and during an initial portion of its power stroke, a second finger fixedly carried by the hammer and telescoping into said second passageway to restrict flow thereinto during the final portion of the hammers movement in its power stroke and during an initial portion of its return stroke.

22. An impact tool powered by a compressible fiuid which comprises, in combination, anvil means, fiuid supply conduit means haivng a casing portion extending to telescope over one end of the anvil means, means connecting between said anvil means and casing portion permitting limited longitudinal movement while limiting relative rotational movement therebetween, -a hammer having spaced apart piston portions of different effective cross-sectional areas slidably engaging corresponding cylinder portions of said casing portion, a passageway in the hammer having a terminus at the end of the hammer remote from the anvil means and also extending to communicate with the space between the other end of the hammer and the anvil, passageway in the anvil means having a terminus at the end of the anvil means adjacent said other end of the hammer and also communicating with the exterior of the tool, first and second fingers respectively carried by the conduit means and said other end of the hammer and aligned respectively with said termini of said hammer and anvil means passageways to move thereinto upon reciprocation of the hammer and alternately restrict flow therethrough whereby fiuid pressure on said other end of the hammer is alternatively increased and decreased to cause the hammer to reciprocate.

23. An impact tool powered by a compressible fiuid which comprises, in combination, an anvil; a fiuid supply conduit; a hammer mounted for reciprocation between the anvil and conduit to deliver blows to the anvil; the hammer, anvil and conduit together providing upper and lower variable Volume chambers with oppositely facing effective areas on the hammer respectively forming one wall of said chambers and with the upper chamber being in fiuid communication with an inlet to said conduit; first and second passageways extending respectively from the first chamber through the hammer to the second chamber and from the second chamber through the anvil to the exterior of the tool; a valve element carried by the conduit and operable to restrict fiow through said first passageway while the hammer is moving through an initial portion of its power stroke and to open said first passageway upon the hammer striking the anvil; a finger fixedly carried by the hammer and telescoping into the second passageway 1,665,046 Tucker Apr. 3, 1928 to restrict ow therethrough while the hammer is less than 1,861,042 Zublin May 31, 1932 a predetermined distance from the anvil and being moved 1,881,258 Bayles Oct. 4, 1932 from the second passageway to open the same to fluid 1,892,517 Pennington Dec. 27, 1932 ow upon the hammer moving away from the anvil far- 5 2,033,527 Kitching Mar. 10, 1936 ther than said predetermined distance. 2,085,279 Tautenhahn June 29, 1937 2,326,383 Morrison Aug. 10, 1943 References Cited 1n the file of th1s patent 2,563,083 Topanelian Aug. 7! 1951 UNITED STATES PATENTS Y 2,580,203 Topanelian Dec. 25, 1951 1,096,886 Bayles May 19, 1914 10 2,665,115 Bassinger Jan. 5, 1954 1,518,124 Mercer Dec. 2, 1924 2,756,723 Bassinger July 31, 1956 

